The present invention relates to a fabrication control system and particularly to a fabrication control system capable of controlling fabrication backup applied in multiple fabrication facility locations.
FIG. 1 is a schematic view showing a conventional fabrication system 100, capable of fabricating semiconductor wafers, and containing Fabs 11 and 13. Fabs 11 and 13 are not identical in tool composition, but have similar and/or partially overlapping tool sets. Fabs 11 and 13 contain tools 11a˜11n and 13a˜13n respectively. Tools 11a˜11n and 13a˜13n are controlled by Manufacturing Execution Systems (MESs) 110 and 130 respectively. Although both Fabs 11 and 13 belong to fabrication system 100, they are not only geographically separated but also operate discretely. Because of the discrete operation, workloads allocated to Fab 11 cannot be processed in Fab 13, and vice versa. Even though Fab 13 is available for providing backup operation, Fab 11 loading must wait for processing when a bottlenecked tool is backed up. Thus, some tools in Fab 13 may remain idle despite Fab 11 having wafer lots queued at a corresponding tool. The independent operation of Fabs 11 and 13 actually hinders fabrication system 100 from optimizing utilization.
While cross-Fab backup within a fabrication system is clearly desired, it is not routinely practiced due to great difficulty in monitoring and controlling a plurality of separately located independent fabrication facilities. Cross-Fab backup is presently executed manually in the conventional fabrication system, an inefficient and mistake-prone process. Moreover, owing to the complexity of wafer fabrication, the conventional cross-Fab backup cannot address every detail of process operation, resulting in yield loss. In U.S. patent application Ser. No. 20020165629 (Backup control system for optimizing utilization of multiple fabrication facilities), Ho et al. disclose a backup control system and method for monitoring and controlling multiple fabrication facilities. The above-mentioned invention relieves the manual burden of conventional cross-Fab backup and enhances the overall utilization of the multiple fabrication facilities.
In wafer fabrication processes, however, most work-in-process (WIP) has manufacturing constraints, based on process time, equipment, Advance Process Control (APC), and contamination. These manufacturing constraints are set to prevent mis-operation and yield loss. Both the conventional method and the cited disclosure fail to relay these manufacturing constraints between Fabs during cross-Fab backup, thereby increasing the likelihood of mis-operation and yield loss, and thus counteracting the benefits of cross-Fab backup operation.
Hence, there is a need for a fabrication system that addresses mis-operation during cross-Fab backup arising from the existing technology.